| In recent years, with the expansion of enrollment scale in colleges and universities, the population density has increased, and the green area has amplified. In addition, the water consumption in colleges and universities has increased year by year, which become the major water consumers in urbans of our country. On the other hand, due to the many colleges and universities are built in the suburbs, far from the municipal sewage pipe, a large number of untreated sewage discharge directly, which will pose a threat to the local environment.Therefore, it is urgent to strengthen college sewage treatment and realize campus water reuse for the sustainable development in colleges and universities.Although many water treatment systems have been built in colleges and universities, a larger area, higher operating costs, and more complex technology are needed, which limited the operation of these systems. Additionally, the water quality cannot achieve "reuse of urban recycling water—water quality standard for industrial uses". To seek an advanced treatment is needed after the conventional water treatment process to guarantee the final effluent indexes. Constructed wetland is a new type of wastewater treatment technology, due to its low cost, easy operation and low maintenance. Therefore, it has very important significance to focus on the study of constructed wetland as a depth processing unit in campus sewage treatment systems.The objective of this study was to investigate the water quality of campus sewage in some university in Shandong. Results showed that all the parameters including COD (160-184mg/L), TN(47.9-68.2mg/L), TP (0.87-2.49mg/L), and NH3-N (27.0-40.0mg/L) were higher than the water quality of effluent met the urban sewage treatment plant pollutant discharge standard (GB18918-2002). Three pilot scale systems were built to simulate constructed wetlands as the depth of processing units, to deal with secondary effluent. After a period of time, the COD was less than50mg/L, and TP was less than0.5mg/L, which were superior to the water discharge standards (A level). However, the nitrogen removal is still not reach the standards. In this study, the immobilization of Paenibacillus lautus CL5and its application in constructed wetland for schoolyard domestic sewage treatment were investigated. Polyurethane sponge was chosen as support for the immobilization of Paenibacillus lautus CL5. Three pilot scale systems were built to simulate constructed wetlands: A(control), B (Bioaugmentation by bacterium suspension), and C(Bioaugmentation by immobilized bacterium). Results revealed that:(1) CL-5strains was gram-negative bacteria, bacillus,(0.26-0.31)×(1.55-2.50) μm, with no flagella. N2was the end gas product of this denitrifying phosphorus accumulating bacteria. By16s rRNA sequencing, the sequence homology comparison analysis indicated that CL-5was Paenibacillus lautus.(2) Polyurethane sponge was chosen as support for the immobilization of Paenibacillus lautus CL5. Results showed that the immobilized denitrifying bacteria had effective removal for COD and nitrogen in wastewater. The optimum doseage was seven per500ml water (volume ratio,25%), and the optimal carbon/nitrogen ratio was4. The greatest removal rate of COD, TN and nitrate nitrogen were63%,96%and97%, respectively.(3) In the optimal experimental conditions, the removal efficiency was stable with the immobilized strains. The removal rate of COD, TN, and NO3-N were38%-56%,68%-79%, and82%-89%respectively.There is no accumulation of nitrite nitrogen in reaction process.(4) The optimal hydraulic retention time was5d. The water quality of effluent met the urban sewage treatment plant pollutant discharge standard (GB18918-2002) and the reuse of urban recycling water—water quality standard for industrial uses (GB T18921-2002). A steady performance was achieved through5cycles of continuous running.(5) Bioaugmentation in constructed wetland would be a cost-effective measure for schoolyard domestic sewage treatment, which can serve as a kind of advanced treatment process. |
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